WO1991002767A1

WO1991002767A1 - Polyolefin-polyester graft polymers with high graft ratio

Info

Publication number: WO1991002767A1
Application number: PCT/US1990/004822
Authority: WO
Inventors: Yuji Fujita; Shigeyuki Toki
Original assignee: Tonen Corporation
Priority date: 1989-08-24
Filing date: 1990-08-24
Publication date: 1991-03-07
Also published as: AU6295990A

Abstract

The invention provides novel copolymers of polyesters and polyolefins with high graft ratios and processes for producing these graft copolymers. The processes include grafting reactive groupings such as carboxyl or epoxy groups onto the polyolefin and reacting these with hydroxyl groups on the polyesters to form high graft ratio copolymers. In one aspect, the process uses a heat treatment to produce the high graft ratio, in another it uses an acid catalyst.

Description

POLYOLEFIN-POLYESTER GRAFT POLYMERS

WITH HIGH GRAFT RATIO

SPECIFICATION

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for producing a polyolefin-polyester graft copolymer which is effective as a compatibilizer for a resin composition composed of polycarbonates (or other engineering plastics) and polyolefins. More particularly, it is related to a process for producing a graft copolymer, having a high graft ratio, from a polyester and a modified polyolefin.

2. Description of the Related Art

Aromatic polycarbonates have the disadvantages of being poor in solvent resistance and moldability despite their good impact resistance, heat resistance, stiffness, and dimensional stability. Many attempts have been made to blend polycarbonates with a polyolefin to produce a polycarbonate composition free of these disadvantages while retaining good, balanced mechanical properties. Unfortunately, the compatibility of polycarbonates with polyolefins is not good. Efforts have therefore been directed at improvement in compatibility by the incorporation of a third component.

Examples of the third components incorporated into the composition of polycarbonate resin and polyolefin resin are: butyl rubber (as disclosed in Japanese Patent Laid-Open No. 108151/1982), ethylene-propylene copolymer and/or ethylene-propylene-diene copolymer (as disclosed in Japanese Patent Laid-open No. 108152/1982), and isoprene rubber and/or methylpentene polymer (as disclosed in 111351/1982).

These third components, however, are not necessarily satisfactory as a compatibilizer for polycarbonate and polyolefin resins. They have a severe disadvantage in that they substantially reduce the impact resistance of moldings and cause peeling of the surface when the content of polyolefin is high.

A variety of compositions composed of an aromatic polycarbonate and a polyester and/or modified polyolefin have also been produced. (See Japanese Patent Laid-Open Nos. 225245/1986, 235456/1986, and 238847/1986.) These compositions, however, are poor in solvent resistance because of their lack of polyolefin content.

Other attempts include a thermoplastic resin composition composed of 100 parts by weight of aromatic polycarbonate (95-5 wt%) and polyolefin (5-95 wt%), 2-100 parts by weight of modified polyolefin, and 2-100 parts by weight of polybutylene terephthalate. (See Japanese Patent Laid-Open No. 75547/1989) In this composition the modified polyolefin and polybutylene terephthalate form a graft copolymer which produces good compatibility between the aromatic polycarbonate and the polyolefin.

The present inventors previously proposed a process for producing a polyolefin-polyester graft copolymer as a good compatibilizer for polycarbonate resin and polyolefin, by reacting 15-85 parts by weight of polyester and 85-15 parts by weight of modified polyolefin at 260-320°C using a twin-screw extruder, said polyester having an intrinsic viscosity [η] of 0.30-1.20 and containing 15-200 meq./kg of terminal carboxyl groups and said modified polyolefin containing 0.2-5 mole % of epoxy groups and having a weight-average molecular weight of 8000-140,000. (See Japanese Patent Application No. 258883/1988.)

Moreover, the present inventors previously proposed a process for producing a polyolefin- polyester graft copolymer that can be used as a good compatibilizer for polycarbonate resin and polyolefin, by reacting 10-90 parts by weight of polyester and 90- 10 parts by weight of modified polyolefin at 260-320°C in a molten mixture state, said polyester having an intrinsic viscosity [η ] of 0.50-1.80 and containing 10-100 meq./kg of terminal carboxyl groups and said modified polyolefin containing 0.2-5 mol% of carboxyl groups or epoxy groups and having a weight-average molecular weight of 8000-140,000, said reaction being carried out in the presence of 0.05-2.0 parts by weight of water for 100 parts by weight of the total amount of said polyester and modified polyolefin. (See Japanese Patent Application No. 98564/1989.)

While the polyolefin-polyester graft copolymers disclosed in said Japanese Patent Application Nos. 258883/1988 and 98564/1989 improve the compatibility of polycarbonate resin and polyolefin, it was found that to produce a more effective compatibilizer, it is necessary that the graft copolymer have a higher graft ratio. One possible way of achieving this is to increase the grafting reaction rate so that the residue of undesirable unreacted polymer is minimized. Similarly, in the case of the thermoplastic resin composition disclosed in Japanese Patent Laid-Open No. 75547/1898, it would also be desirable to increase the graft ratio of the graft copolymer of modified polyolefin and polybutylene terephthalate to be formed. While this need to achieve a higher graft ratio exists, a method for producing higher graft ratios has not heretofore been known.

SUMMARY OF THE INVENTION

The present invention provides processes for producing high graft ratio polyolefin-polyester copolymers from a modified polyolefin and a polyester. According to one aspect of the invention process, the graft ratio is greatly increased when a polyester and modified polyolefin are melt-mixed together and the resulting product is heat-treated for a long time under an inert gas stream. More particularly, this aspect of the invention process comprises the steps of (a) melt-mixing 2-98 parts by weight of polyester and 98-2 parts by weight of modified polyolefin containing carboxyl groups or epoxy groups, and (b) subjecting the mixture to heat treatment for 1-100 hours at a temperature 40-150°C lower than the melting point of said polyester. While not wishing to be bound by any theory, it is speculated that heat treatment promotes the reaction between the carboxyl or epoxy groups in the modified polyolefin and the terminal hydroxyl group on the polyester.

In another aspect of this invention, the graft ratio is greatly increased if a graft copolymer is produced by the reaction of a polyester with a modified polyolefin in the presence of an acid catalyst. In this aspect, the invention process for producing a polyolefin-polyester graft copolymer comprises reacting 2-98 parts by weight of polyester with 98-2 parts by weight of a modified polyolefin containing carboxyl groups or epoxy groups in the presence of an acid catalyst, the catalyst being present in an amount of 0.01-5 parts by weight for each 100 parts by weight of said polyester and modified polyolefin. Again, while not wishing to be bound by any theory, it is speculated that the acid promotes the reaction between the carboxyl or epoxy group of the modified polyolefin and the terminal hydroxyl group of the polyester.

The invention product, a high graft ratio copolymer of a polyester and a polyolefin, is especially useful as a compatibilizer in resin compositions that include polyolefins and polycarbonates (or other engineering plastics).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polyester used in the present invention is usually a thermoplastic resin composed of a saturated dicarboxylic acid and a saturated dihydric alcohol. It includes, for example, polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate (polybutylene terephthalate), polyhexamethylene terephthalate, polycyclohexane-1,4- dimethylol terephthalate, and polyneopentyl terephthalate. Preferable among them are polyethylene perephthalate and polybutylene terephthalate. The useful polyesters also include polycaprolactone and polyvalerolactone, which are polymers of lactone. Preferable among these is polycaprolactone.

The polyester should preferably have an intrinsic viscosity [η] of 0.5-1.8 and contain 1-100 meq./kg of terminal carboxyl groups. (The intrinsic viscosity

[η] (dl/g) is one which is obtained from the solution viscosity in o-chlorophenol at 25°C.) With an intrinsic viscosity [η] lower than 0.5, the polyester does not significantly improve the compatibility. With an intrinsic viscosity [η] higher than 1.80, the polyester gives rise to a reaction product which has too high a melt viscosity for ease of processing. With a terminal carboxyl group content less than about 5 meq./kg, the polyester reactivity with the modified polyolefin is poor. With a content of terminal carboxyl groups in excess of 100 meq./kg, the polyester is too reactive with the modified polyolefin and tends to form a gel.

For one of the preferred polyesters, polyethylene terephthalate, the intrinsic viscosity [η] should preferably be 0.50-1.0 and the content of terminal carboxyl groups should preferable be 5-100 meq./kg. With an intrinsic viscosity higher than 1.0, the polyethylene terephthalate gives rise to a graft copolymer which has a high melt viscosity and forms gel. The polyethylene terephthalate may have the terephthalic acid component which is substituted by an alkyl group or halogen group; and it may also have the glycol component which contains, in addition to ethylene glycol, up to about 50 wt% of other glycols such as 1,4-butylene glycol, propylene glycol, and hexamethylene glycol.

For the preferred polybutylene terephthalate, the intrinsic viscosity [n] should preferably be 0.5-1.8 and the content of terminal carboxyl groups should preferably be 5-100 meq./kg. As with the preferred polyethylene terephthalate, the polybutylene terephthalate may have the terephthalic acid component which is substituted by an alkyl group or halogen group; and it may also have the glycol component which contains, in addition to 1,4-butylene glycol, up to about 50 wt% of other glycols such as ethylene glycol, propylene glycol, and hexamethylene glycol.

The polycaprolactone should preferably have a number-average molecular weight (M_n) of 500-200,000 and contain 5-2000 meq./kg of terminal carboxyl groups.

The modified polyolefin used in the present invention is a polyolefin formed by its copolymerization with unsaturated monomers having a carboxyl group or epoxy group. The unsaturated monomer having a carboxyl group is an unsaturated carboxylic acid itself or its anhydride. These include monocarboxylic acids (such as acrylic acid and methacrylic acid), dicarboxylic acids (such as maleic acid, fumaric acid, and itaconic acid), and dicarboxylic acid anhydrides (such as maleic anhydride and itaconic anhydride). Preferable among these are the dicarboxylic acids and their anhydrides. Examples of unsaturated monomers having an epoxy group include glycidyl methacrylate and glycidyl acrylate.

The unsaturated monomer having a carboxyl group or epoxy group is copolymerized with an olefin, such as, ethylene, propylene, butene-1, and pentene-1. These olefins may be used alone or in combination with one another. These olefins may further be incorporated with less than 10 wt% of monomer (such as vinyl acetate, isoprene, chloroprene, and butadiene), according to need. Preferable among these modified polyolefins are copolymers of ethylene with acrylic acid, maleic anhydride, or glycidyl methacrylate.

The modified polyolefin containing carboxyl groups or epoxy groups may be in the form of block copolymer, graft copolymer, random copolymer, or alternating copolymer. In the case of a graft copolymer, graft copolymerization should preferably be carried out by melt-mixing a polyolefin (which functions as the main chain) with the above-mentioned unsaturated monomer.

The above-mentioned modified polyolefin should preferably have a weight-average molecular weight of 8,000-300,000 and contain 0.1-20 mol% of carboxyl groups or epoxy groups, where the weight-average molecular weight is measured by gel permeation chromatography (GPC) and expressed in terms of unmodified polyolefin. The content of carboxyl groups is obtained by elemental analysis, and the content of epoxy groups is obtained by oxygen analysis. With a weight-average molecular weight lower than 8,000, the modified polyolefin does not produce a significant improvement in compatibility. Conversely, with a weight-average molecular weight in excess of 300,000, the modified polyolefin has such a high melt viscosity than it is poor in moldability. With a content of carboxyl groups or epoxy groups less than 0.1 mole%, the modified polyolefin is so low in reactivity with the polyester that it does not form the graft copolymer easily. With a content of carboxyl groups or epoxy groups in excess of 20 mol%, the modified polyolefin is excessively reactive with the polyester and gives rise to a reaction product which has a high melt viscosity and forms gel.

In one aspect of the invention process, the graft polymerization of said polyester and said modified polyolefin may be accomplished by the dry-blending of the two and subsequent melt-mixing. The melt mixing should preferably be performed at about 260-320°C for about 0.5-1.5 minutes in an extruder, particularly in a twin-screw extruder. When the reaction temperature is lower than about 260°C, grafting does not take place sufficiently. At a reaction temperature higher than about 320°C, reactions take place excessively, resulting in the clogging of the extruder due to gel formation. Excessive reactions also lead to the deterioration of resins.

The polyester and modified polyolefin should be used in an amount of about 2-98 parts by weight, preferably about 20-80 parts by weight, for the former and about 98-2 parts by weight, preferably about 80-20 parts by weight, for the latter. If the amount of the polyester is less than about 2 parts by weight or more than about 98 parts by weight, the graft copolymer forms in a lesser amount.

The mixture of said polyester and said modified polyolefin is heat treated for about 1-100 hours in an inert atmosphere at a temperature about 40-150°C, lower than the melting point of the polyester to increase the graft ratio.

When the heat treatment temperature is higher than the melting point of the polyester minus about 40°C, the heat treatment will cause pellets to melt, when the heat treatment temperature is lower than the melting point of the polyester minus about 150°C, the heat treatment does not produce a significant effect in increasing the graft ratio. When the polyester is polyethylene terephthalate, the preferred heat treatment temperature is in the range of about 120- 230°C.

The heat treatment time varies depending on the heat treatment temperature. When the heat treatment time is less than one hour, the heat treatment does not produce a significant effect in increasing the graft ratio. Conversely, the graft ratio does not increase any further when the heat treatment lasts for more than 100 hours. Thus, a preferred heat treatment time ranges from about 5 to about 50 hours. The inert atmosphere in which said heat treatment is performed is an atmosphere which brings about substantially no deterioration of the mixture. These atmospheres include inert gas (such as argon), non-reactive gas (such as nitrogen and hydrogen), and vacuum atmospheres. Heat treatment in a nitrogen stream is preferable from a practical point of view. For efficient heat treatment, the mixture should preferably be in the form of granules, like pellets.

According to another aspect of the invention process, an acid catalyst is added to the polyester and modified polyolefin. The acid catalyst is any acid which functions as a catalyst. It includes, for example, sulfuric acid, phosphoric acid, hydrofluoric acid, and organic sulfonic acid. Preferable among them is an organic sulfonic acid, particularly p- toluenesulfonic acid.

The graft polymerization of said polyester and said modified polyolefin may be accomplished by the melt-mixing method or solution method.

The melt-mixing acid-catalyzed method may be practiced by mixing the polyester, modified polyolefin, and acid catalyst in the heated state using a mixer, such as, single-screw extruder, twin- screw extruder, Banbury mixer, mixing roll, Brabender, and kneader. The mixing should last for about 0.5-15 minutes at about 180-320°C, depending on the melting point of the polyester used. Mixing in a twin-screw extruder is preferable. At a reaction temperature lower than about 180°C, grafting does not take place sufficiently due to insufficient polymer melting. At a reaction temperature higher than 320°C, reactions take place excessively, resulting in the clogging of the extruder due to gel formation. Excessive reactions lead to the deterioration of resins.

The solution method may be practiced by stirring a solution of said starting materials in an organic solvent, such as for example xylene, at about 80- 140°C. When the reaction temperature is lower than about 80°C, grafting does not take place sufficiently. When the reaction temperature is higher than about 140°C. grafting also does not take place because the solvent boils.

In the acid-catalyzed process, the polyester and modified polyolefin should be used in an amount of about 2-98 parts by weight, preferably about 20-80 parts by weight, for the former and about 98-2 parts by weight, preferably about 80-20 parts by weight, for the latter. If the amount of the polyester is less than about 2 parts by weight or more than about 98 parts by weight, the graft copolymer forms in a lesser amount.

The acid catalyst should be added in an amount of 0.01-5 parts by weight, preferably 0.1-3 parts by weight, for 100 parts by weight of the total amount of the polyester and modified polyolefin. With an amount less than 0.01 parts by weight, the acid catalyst does not produce a good effect of increasing the graft ratio. With an amount more than 5 parts by weight, the acid catalyst forms gel due to excessive reactions.

The polyolefin-polyester graft copolymers obtained from the invention processes have a high graft ratio and are suitable for use as compatibilizers for engineering plastics (such as polycarbonates and polyolefins). Usually, the graft copolymer is incorporated in an amount of 1-30 parts by weight for 100 parts by weight of the total amount of the two.

In the specification and claims, the term "pbw" means "parts by weight."

The following examples serve to illustrate the invention and are not to be construed as limiting the invention as described above and claimed hereafter.

The components used in the following Examples are listed below for ease of reference:

(1) Polyesters

PET: Polyethylene terephthalate (TR4550), made by Teijin Kasei, having a weight- average molecular weight of 104,000 and an intrinsic viscosity [η] of 0.7, and containing 35 meq./kg of terminal carboxyl groups. PBT: Polybutylene terephthalete (TRB-K), made by Teijin Kasei, having a weight- average molecular weight of 38,000 and an intrinsic viscosity [η] of 0.73, and containing 60 meq./kg of terminal carboxyl groups.

PCL: Polycaprolactone, made by Scientific Polymer Products, Inc., having a weight- average molecular weight of 23,000.

(2) Modified polyolefins

Modified PO (1): A copolymer of glycidyl methacrylate and ethylene ("Bondfast E") made by Sumitomo chemical Co., Ltd., containing 4.0 mol% of glycidyl methacrylate and having a weight-average molecular weight of 263,000.

Modified PO (2) : A copolymer of acrylic acid and ethylene ("Primacol 3440") made by

Dow Chemical Co., Ltd., containing 5.3 mol% of acrylic acid and having a weight-average molecular weight of 72,000.

Modified PO (3) : A graft copolymer of polypropylene with maleic anhydride, containing 0.25 mol% of maleic anhydride and having a weight-average molecular weight of

133,000.

(3) Acid catalyst P-TSA: p-ptoluenesulfonic acid (reagent grade), made by Tokyo Kasei Co., Ltd.

H₂SO₄: Sulfuric acid (reagent grade), made by Tokyo Kasei Co. , Ltd.

The weight-average molecular weight is one which is measured by the GPC method, and it is expressed in terms of polyethylene for the modified PO (1) and modified PO (2) and in terms of polypropylene for the modified PO (3).

Examples 1 to 4

The polyester and modified polyolefin were dry blended at a ratio of 30/70 (by weight) as shown in Table 1, and the dry blend was made into pellets by melt mixing at 280°C and 200 rpm using a 45-mm twin-screw extruder. The resulting pellets underwent heat treatment at 170°C for 24 hours under a nitrogen stream. The copolymer was tested for graft ratio A.

Graft ratio A is expressed in terms of the ratio

(wt%) of insoluble matter separated as the graft copolymer when the copolymer is dissolved in m-cresol

(at 100°C) and xylene (at 100°C). The results are shown in Table 1.

Comparative Examples 1 and 2

The procedures of Examples 1 and 2 were repeated except that the heat treatment was not performed, the resulting copolymers were tested for graft ratio. The results are shown in Table 1. TABLE 1

Example (Comparative Example) 1 2 3 4 (1) (2)

Polyester, PET 30 - - 30 30 30 - -

Polyester, PBT - - 30 - - - - - - 30

Modified Polyolefin, PO(1) 70 70 - - - - 70 70

Modified Polyolefin, PO(2 ) - - - - 70 - - - - - -

Modified Polyolefin, PO(3 ) - - - - - - 70 - - - -

Heat Treatment Yes Yes Yes Yes No No

Graft Ratio (wt%) 42 45 38 10 28 32

Examples 5 to 9

The polyester (polyethylene terephthalate or polybutylene terephthalate) and the modified polyolefin (1) were dry-blended in a ratio of 30/70 or 50/50 (by weight) together with p-toluenesulfonic acid as the acid catalyst as shown in Table 1. The dry blend underwent melt mixing for grafting reaction at 280°c and 200 rpm using a 45-mm twin-screw extruder. The resulting polyolefin polyester graft copolymer was tested for graft ratio (graft ratio A).

The results are shown in Table 2.

Comparative Examples 3 and 4

The procedure of Examples 5 and 8 were repeated except that no acid catalyst was added. The resulting copolymers were tested for graft ratio A. The results are shown in Table 2.

Examples 10 and 11

A total of 2 g of polycaprolactone and modified polyolefin (3) in a ratio of 70/30 (by weight), were reacted in 50 g of boiling xylene for 10 hours under a nitrogen stream, in the presence of p-toluenesulfonic acid (in an amount as shown in Table 2 for each 100 parts by weight of the total amount of polycaprolactone and modified polyolefin).

The reaction mixture was poured into methanol to precipitate the polymer formed by the reaction. The precipitates were filtered off and dried at 60ºC for 12 hours in a vacuum oven to obtain the polyolefin-polyester graft copolymer.

The resulting polyolefin-polyester graft copolymer was tested for graft ratio (graft ratio B).

Graft ratio B is calculated by the following formula from xylene insolubles which remain after the separation of unreacted polycaprolactone (soluble in xylene) from the reaction product.

Graft ratio

where: X is the amount of xylene insolubles, and

Y is the amount of modified polyolefin (3) used.

Comparative Example 5

The procedure of Example 9 was repeated except that no acid catalyst was added. the resulting copolymer was tested for graft ratio B. The results are shown in Table 2.

Examples 12 to 14

The polycaprolactone and the modified polyolefin (3) were melt-mixed for grafting reaction in a ratio of 70/30 (by weight) together with p-toluenesulfonic acid or sulfuric acid as the acid catalyst using a Brabender at 200°C and 60 rpm for 10 minutes, as shown in Table 2. The resulting polyolefin-polyester graft copolymer was tested for graft ratio B. The results are shown in Table 2.

Comparative Example 6

The procedure of Example 12 was repeated except that no aid catalyst was added. The resulting copolymer was tested for graft ratio B. The results are shown in Table 2.

Although the invention has been described with reference to its preferred embodiments, those of ordinary skill in the art may, upon reading this disclosure, appreciate changes and modifications which do not depart from the scope and spirit of the invention as described above or claimed hereafter.

Claims

CLAIMS:

1. A process for preparing a polyolefin-polyester graft copolymer, comprising:

(i) mixing from about 2 to about 98 pbw of polyester with from about 98 to about 2 pbw of a modified polyolefin wherein said modified polyolefin includes carboxyl or epoxy groups;

(ii) heating the mixture for from about 1 to about 100 hours at a temperature from about 40 to about 150°C lower than the melting point of said polyester.

2. The process of claim 1 wherein the modified polyolefin comprises a polyolefin modified with from about 0.1 to about 20 mol% of an unsaturated carboxylic acid, an anhydride of an unsaturated carboxylic acid, or an epoxy-group-containing composition.

3. The process of claim 1 or 2 wherein the heating of the mixture is for from about 5 to about 50 hours.

4. The process of claim 1 or 2 wherein said mixing is under conditions of meltblending.

5. The process of claim 1 wherein said mixing comprises mixing from about 20 to about 80 pbw of polyester with from about 80 to about 20 pbw of a modified polyolefin under melt blending conditions and said heating is for from about 5 to about 50 hours.

6. A process for producing a polyolefin-polyester graft copolymer, comprising:

reacting from about 2 to about 98 pbw of polyester with from about 98 to about 2 pbw of modified polyolefin in the presence of an acid catalyst,

wherein said catalyst is present in an amount from about 0.01 to about 5 pbw for each 100 parts of polyester and polyolefin, and wherein said modified polyolefin includes carboxyl or epoxy groups.

7. The process of claim 6 wherein said reacting is under melt blending conditions.

8. The process of claim 6 wherein said reacting is carried out in a suitable common solvent.

9. The process of claim 7 or 8 wherein said modified polyolefin comprises a polyolefin modified with from about 0.1 to about 20 mol% of an unsaturated carboxylic acid, the anhydride of a carboxylic acid, or an epoxy-group-containing composition.

10. The process of claim 7 or 8 wherein the acid catalyst is p-toluenesulfonic acid or sulfuric acid.

11. A graft copolymer of a polyester and a modified polyolefin having a graft ratio of at least about 7 wt%.

12. The graft copolymer of claim 11 wherein the polyester is a polycaprolactone, the modified polyolefin is polypropylene modified with maleic anhydride, and the graft ratio is graft ratio B.

13. The graft copolymer of claim 11 wherein the graft ratio is graft ratio A and the graft ratio is at least about 45 wt%, the modified polyolefin is a copolymer of glycidyl methacrylate and ethylene, and the polyester comprises polybutylene terephthalate or polyethylene terephthalate.

14. A graft copolymer of a polyester and a modified polyolefin wherein said copolymer has been heat treated for from about 1 to about 100 hours and wherein said copolymer has a graft ratio of at least about 10 wt%.

15. The graft copolymer of claim 14 wherein the polyester comprises polyethylene terephthalate or polybutylene terephthalate and the modified polyolefin comprises a glycidylmethacrylate ethylene copolymer, an acrylic acid ethylene copolymer, or a maleic anhydride propylene copolymer.

16. The process of claim 7 or 8 wherein the reacting comprises reacting from about 20 to about 80 pbw of polyester with from about 80 to about 20 pbw of a modified polyolefin, said polyolefin being modified by the addition of about 0.1 to about 20 mole% of an unsaturated carboxylic acid, an anhydride of a carboxylic acid or an epoxy-group-containing composition.